Images and graphics have been directly screen printed onto plastic surfaces, such as basketball backboards. Some plastic surfaces accept printing ink more readily than others. For example, it is easier to print on polystyrene than on polyolefin surfaces.
In a typical screen printing process on polyolefin surfaces, such as a molded basketball backboard, the product is placed onto a conveyor. Dust and debris are removed from the surface using an air knife. The surface is then flame treated to increase the surface energy of the backboard substrate which will allow the ink to adhere to its surface.
A printer manually loads the product into a nested fixture. The surface is screen printed, and the conveyor moves the product into an oven at about 200.degree. F. (93.degree. C.) for about 35 seconds to heat cure the ink. The printer then repeats the foregoing process steps to add further color images. Finally, the product is removed from the conveyor and allowed to air dry.
In the current screen printing process on plastic surfaces, a 230 mesh screen is used, resulting in a dpi (dots per inch) resolution of between 12 and 15. It has been found that the typical solvent-based printing inks dry out quickly on full flood prints, usually after 10 to 20 passes. When the ink drys on the printing screen, inconsistent printing of poor quality results.
Regrettably, the oven heat used to heat cure the ink alters the size of a typical basketball backboard by as much as 1/4 inch. This 1/4 inch size change makes it very difficult or impossible to properly align additional printing screens for multicolor printing. Thus, the resolution on plastic surfaces, such as basketball backboards, using conventional screen printing processes is inadequate.
It would be an advancement in the art to provide a system for direct, multi-color printing on basketball backboards and other plastic surfaces which eliminate the problems relating to flame treating the printing surface and heat-cured inks described above.